For example, a water electrolysis device is used to produce a hydrogen gas as a fuel gas for a power generation reaction in a fuel cell. The water electrolysis device contains a solid polymer electrolyte membrane for decomposing water to generate the hydrogen (and oxygen). Electrode catalyst layers are disposed on either side of the solid polymer electrolyte membrane to form a membrane-electrode assembly, and current collectors are disposed on either side of the membrane-electrode assembly to form a unit.
A plurality of the units are stacked, a voltage is applied to the stacking-direction ends, and the water is supplied to the anode-side current collector. Then, the water is decomposed to generate hydrogen ions (protons) at the anode side of the membrane-electrode assembly. The hydrogen ions are transferred through the solid polymer electrolyte membrane to the cathode side, and bonded with electrons to produce the hydrogen. Meanwhile, at the anode side, the oxygen generated simultaneously with the hydrogen is discharged together with the residual water from the unit.
Known water electrolysis devices include high-pressure hydrogen production devices capable of generating a high-pressure hydrogen (at a pressure of several tens MPa) at the cathode side. For example, as shown in FIG. 7, a high-pressure hydrogen production device disclosed in Japanese Laid-Open Patent Publication No. 2006-070322 contains a cathode current collector 2 and an anode current collector 3 disposed on either side of a solid polymer membrane 1, separators 4a and 4b, and flow paths 5a and 5b. When water is supplied to the flow path 5b in the anode-side separator 4b and the current collectors 2 and 3 are energized, the water is electrolyzed to generate the high-pressure hydrogen gas in the flow path 5a in the cathode-side separator 4a 
The high-pressure hydrogen production device further contains a disc spring 6 as a pressing means for pressing the cathode current collector 2 into tight contact with the solid polymer membrane 1. The disc spring 6 is disposed in the flow path 5a to press the cathode current collector 2 toward the solid polymer membrane 1. Therefore, the contact resistance between the solid polymer membrane 1 and the cathode current collector 2 is not increased even under the high pressure at the cathode side.